GM/Ford? based armoured vehicles of the Dutch East Indies

[nuyt]

Hello,
I need your help identifying this Chevrolet cowl.
The pic was presumably taken in the last months of 1940 and shows the GM assembly plant at Priok, Java.

I think this truck (or chassis/cab) is a Chevrolet COE, possibly of the types used to build overvalwagens.
Can anybody confirm this and identify the model year (1940?) or type (WE?)?

(picture from bandjir)

Kind regards,
Nuyt